02WS6FREEBIRD

iTrader: (4)

Hey

I would like to know what is the best spark to net the highest mileage in the cruising cells only.

For my A-4, I am in cell 0.20 at 1800 rpm in 4th gear lockup at approx. 55 mph, and I would like to know what would be the best spark to net the best mileage,I know I can try for myself but hope someone has already done this, a local tuner said the highest you could go with a smooth running engine with no knock should like the least amount of fuel (I was at 40 and tried moving my spark up to 44 and didn't see really any increase, still around 17 mpg according to the pid by Soundengineer) is the highest spark the best for mileage at a steady cruising rpm?

There are threads about gas mileage, but have not seen anything about this.

I hope someone has tried or knows about this and will share his thoughts.

Thanks

brianfromhawaii

iTrader: (3)

more spark with no knock is more power on the same amount of fuel... so... you figure it out everyones car is different, i mean my car can handle a fuckload of spark.... doesnt mean yours can

WeathermanShawn

iTrader: (1)

I have played around with 40-44 degrees of spark advance in the low-load cruising cells (M6).

In reality I did not notice any change in gas mileage. I just did it to see how it affected light cruise and decel.

With a high-performance cammed V-8, you are looking at a very small return playing around with spark to get a a couple of more miles out of a tank of gas.

You could lean it out..similar to lean cruise with the proper tuning software. Not something I would ever do to my car, but I understand your dilemma.

It is mainly your driving habits that will affect gas mileage. You may not be in the same situation, but having a second car that gets better mileage makes life a lot easier.

Good luck.

..WeathermanShawn..

macca_779

That is so far from the truth its not funny. Advance just prior to knock is not where mean best torque is. If it was then any retard could tune a timing table. For the low load cruising segments the range between MBT and Knock is quite large.

For finding best spark for fuel economy on the street what I do is play with timing in real time and find where I'm making the most vacuum. Once you find the range of spark that is giving the lowest map pressure go for a number in between the lowest number to get it and the mid most number to get it. That will be as close to MBT as your going to get on the street.

eg if you get a lowest map value of 38kpa between 38-44 degrees which is a 6 degree spread. Use a quarter of it and stick with 39.5 degrees.

Obviously you need to set your fuel first. Try going for about 15.8:1.
And you need a consistent gradient of road and just do it on cruise control.

Mike454SS

iTrader: (4)

However, just going leaner without adding spark...will do almost nothing...so once you get the mixture leaner, then add spark.

16.3:1 is where you will generally find peak efficiency for pump gas (look at the chemistry), and it won't hurt the engine at all at light load to go that lean...as long as you still richen it back up when the airflow comes up...however it will hurt the cats in your car, and the EPA will be very unhappy with you if they catch you.

You might not see a change instantly when datalogging in your MPG...but keep playing with it and then drive a full tank of gas (or 2) normally and see what happens...it's not necessarily just adding spark...and there's no magic number that works on every engine...you need to find what spark produces the optimal burn (most thorough and most properly timed) for the air/fuel mixture in your combustion chambers...it takes a bit of tweaking to find it...but you will.

Doc

iTrader: (9)

Execellent opportunity to sidetrack, anybody aware of what happened in the House of Representatives yesterday?

Or is everybody mourning MJs "untimely" expiration?

People better get off the couch and wake up or, threads about people worring about getting better gas milage in their performance cars are going to be history when all your guns, ****, and hotrods are just locked away in museums all in the name of the myth protecting ourselves from global warming.

Rant off. Please people, call your senators before we have to learn this **** the hard way.

Doc

shoemike

iTrader: (25)

Why waste a dime with a phone call, they don't care what
the constituents want only they're personal ideology.

WeathermanShawn

iTrader: (1)

I have used that technique for finding optimum spark. Interesting, I thought it was kinda of an 'old school' technique, but I am glad to hear other have used it. I just found my car liked higher advance at low-load..ran smoother with 40-44 degrees spark, and yes I saw lower MAP and coolant ECT dropped about 6-8 degrees.

I guess I am somewhat curious on the pursuit of more gas mileage from a high-performance car. Believe me I am not criticizing anyone's motive, but I get 26-28 MPG cruising at 75-80 mph (Colorado 75mph Speed Limit) with 3.90 gears.

Granted you get better gas mileage up here in the thinner air. Perhaps you all can educate me on why the intense interest on gas mileage. I get better highway gas mileage than my 98 Dodge Intrepid.

I am just trying to learn, not criticizing.

Thanks..

..WeathermanShawn..

macca_779

I hate how people say you have a V8 so who cares about economy. Yes I have a V8 and yes I can afford it. But why the hell should I just **** money away when I don't have to. 30+MPG here in a cammed LS1. So I'm having my cake and eating it too. While others with stockers are making less power and drinking more gas.

WeathermanShawn

iTrader: (1)

Yea, I know what you mean Macca.

In the 'old days' when I would fill up at the gas station, bystanders would ask " how much horsepower does that have..or what does it do in the 1/4 mile".

Now they ask "what kind of gas mileage do you get". I think most of them are surprised or do not believe you when you tell them your highway mpg.

Do not misunderstand, wasting money or gas is not smart..I guess I just consider the kind of gas mileage these cars get as phenomenal for the power they produce. They are light, M6's have two overdrives..add some headers and exhaust and most people get even more mpg. I even picked up ~2 more mpg when I added heads.

The only time I approached 30mph on the highway was running really lean (not on purpose). So, I am personally nervous trying to save a few bucks on gas and end up with blowing an engine.

Was just curious, not judging anyone for trying to safely save some gas.

..WeathermanShawn..